This description relates to light condensers.
Light condensers are used for example, in extreme ultra-violet (EUV) lithography systems. In EUV, an EUV light source illuminates a mask having a lithography pattern. The projection optics may take the form of a combination of mirrors used to project an image of the lithography pattern onto a substrate (e.g., a silicon wafer) coated with a layer of photo-resist. The lithography pattern is transferred to the substrate by developing the photo-resist and etching exposed portions of the substrate surface. Because EUV light has a very short wavelength, it can be used to generate patterns on the substrate with very small dimensions. An EUV light source may be a plasma generated by focusing a high-energy laser beam onto a stream of inert gas, such as Xenon, to produce ionized gas molecules. The plasma may also be generated by an electric arc. Light rays are emitted when the ionized gas molecules transition from higher energy states to lower energy states. Plasma sources typically have irregular brightness distributions. For good results in lithography, it is desirable for the light that reaches the substrate to be relatively uniform.